Pre-Socratic philosophy

The knowledge we have of the pre-Socratics derives from accounts, known as doxography, of later philosophical writers (especially Aristotle, Plutarch, Diogenes Laërtius, Stobaeus, and Simplicius), and some early Christian theologians (especially Clement of Alexandria and Hippolytus of Rome). Only fragments of the original writings of the pre-Socratics survive. Many of these are titled Peri Physeos, or On Nature, a title probably attributed later by other authors).[6] The translation of Peri Physeos as On Nature may be misleading: the "on" normally gives the idea of an "erudite dissertation", while "peri" may refer in fact to a "circular approach"; and the traditional meanings of "nature" for us (as opposition to culture, to supernatural, or as essence, substance, opposed to accident, etc.) may be in contrast with the meaning of "physeos" or "physis" for the Greeks (referring to an "originary source", or "process of emergence and development").[7] As all that is available about the pre-Socratics are quotations and testimonies by (often biased) later philosophers and historians, it is sometimes difficult to determine the actual line of argument some pre-Socratics used in supporting their views.

Pre-Socratic philosophy arose from the Ionian Enlightenment, which was a set of advances in scientific thought, explanations on nature, and inquiring into the natural and rational causes behind observable phenomena, that took place in Ionia (archaic eastern Greece) beginning in the 6th century BC. According to C. Stephen Evans, Ionian towns, especially Miletus, had close trade relations with Egypt and Mesopotamia, cultures with observations about the natural world that differed from those of the Greeks, which prompted early Greek thinkers to view them as natural phenomena. Another factor was that these Greek towns were not ruled by autocrats or priests, allowing citizens to freely question a wide range of issues.[8]

Diogenes Laërtius divided the physiologoi into two groups: the Ionian, begun by Anaximander, and the Italiote, begun by Pythagoras.[9]

Modern interest in early Greek philosophy can be traced back to 1573, when Henri Estienne collected a number of pre-Socratic fragments in Poesis Philosophica (Ποίησις Φιλόσοφος).[10] Hermann Diels popularized the term "pre-Socratic" in Die Fragmente der Vorsokratiker (The Fragments of the Pre-Socratics) in 1903. The term "pre-Sokratic" [sic] was used as early as George Grote's Plato and the Other Companions of Sokrates in 1865. Edouard Zeller was also important in dividing thought before and after Socrates.[11] Major analyses of pre-Socratic thought have been made by Gregory Vlastos, Jonathan Barnes, Karl Popper,[12] and Friedrich Nietzsche.[13]

The pre-Socratic philosophers rejected traditional mythological explanations of the phenomena they saw around them in favor of more rational explanations. Their efforts were directed to the investigation of the ultimate basis and essential nature of the external world.[14] Many sought the material principle (archê) of things, and the method of their origin and disappearance.[14] As the first philosophers, they emphasized the rational unity of things and rejected supernatural explanations, instead seeking natural principles at work in the world and human society. The pre-Socratics saw the world as a kosmos, an ordered arrangement that could be understood via rational inquiry.[3] Pre-Socratic thinkers present a discourse concerned with key areas of philosophical inquiry such as being, the primary stuff of the universe, the structure and function of the human soul, and the underlying principles governing perceptible phenomena, human knowledge, and morality.

These philosophers asked questions about "the essence of things":[15]

• From where does everything come?
• From what is everything created?
• How do we explain the plurality of things found in nature?
• How might we describe nature mathematically?

Others concentrated on defining problems and paradoxes that became the basis for later mathematical, scientific, and philosophic study.

The Ionian school was centred in Miletus, Ionia in the 6th century BC. Miletus and its environs was a thriving mercantile melting pot of current ideas of the time.[16] The School included philosophers such as Thales, Anaximander, Anaximenes, Heraclitus, Anaxagoras, and Archelaus.[17] Aristotle called them physiologoi (φυσιολόγοι),[18] meaning "those who discoursed on nature." While some of these scholars are included in the Milesian school of philosophy, others are more difficult to categorize.

The first pre-Socratic philosophers were from Miletus on the western coast of Anatolia. Thales (c. 624 - c. 546 BC) is reputedly the father of Greek philosophy; he declared water to be the basis of all things.[14] Next came Anaximander (610-546 BC), the first writer on philosophy. He assumed as the first principle an undefined, unlimited substance without qualities (apeiron), out of which the primary opposites, hot and cold, moist and dry, became differentiated.[14] His younger contemporary, Anaximenes (585-525 BC), took for his principle air, conceiving it as modified, by thickening and thinning, into fire, wind, clouds, water, and earth.[14]

The Ephesian philosophers were interested in the natural world and the properties by which it is ordered. Xenophanes and Heraclitus were able to push philosophical inquiry further than the Milesian school by examining the nature of philosophical inquiry itself. In addition, they were also invested in furthering observations and explanations regarding natural and physical process and also the functions and processes of the human subjective experience.[19]

Heraclitus and Xenophanes both shared interests in analyzing philosophical inquiry as they contemplated morality and religious belief. This was because they wanted to figure out the proper methods of understanding human knowledge and the ways humans fit into the world. This was much different than natural philosophy that was being done by other philosophers, as it questioned the way the universe operates as well as the place of humans within it.[20]

Heraclitus posited that all things in nature are in a state of perpetual flux, connected by logical structure or pattern, which he termed Logos. To Heraclitus, fire, one of the four classical elements, motivates and substantiates this eternal pattern. From fire all things originate, and return to it again in a process of eternal cycles.

The practical side of philosophy was introduced by Pythagoras (582-496 BC). Regarding the world as perfect harmony, dependent on number, he aimed at inducing humankind likewise to lead a harmonious life. His doctrine was adopted and extended by a large following of Pythagoreans who gathered at his school in south Italy in the town of Croton.[14] His followers included Philolaus (470-380 BC), Alcmaeon of Croton, and Archytas (428-347 BC).

According to one view, the series of thinkers located in Elea (sometimes referred to as the Eleatics, despite the fact that the precise nature of their relationships to one another is not well known) emphasized the doctrine of the One; this is often discussed in terms of the notion of monism.[21] Precisely what this means, however, is a matter for great debate.[21] Xenophanes (570-470 BC) declared a single divinity to be the eternal unity, permeating the universe, and governing it by his thought.[14] Parmenides (510-440 BC) affirmed the one unchanging existence to be alone true and capable of being conceived, and multitude and change to be an appearance without reality.[14] This doctrine was defended by his younger countryman Zeno of Elea (490-430 BC) in a polemic against the common opinion which sees in things multitude, becoming, and change. Zeno propounded a number of celebrated paradoxes, much debated by later philosophers, which try to show that supposing that there is any change or multiplicity leads to contradictions.[14] Melissus of Samos (born c. 470 BC) was another eminent member of this school.

The first explicitly materialistic system was formed by Leucippus (5th century BC) and his pupil Democritus (460-370 BC) from Thrace. This was the doctrine of atoms - small primary bodies infinite in number, indivisible and imperishable, qualitatively similar, but distinguished by their shapes. Moving eternally through the infinite void, they collide and unite, thus generating objects which differ in accordance with the varieties, in number, size, shape, and arrangement, of the atoms which compose them.[14]

Empedocles appears to have been partly in agreement with the Eleatic School, partly in opposition to it. On the one hand, he maintained the unchangeable nature of substance; on the other, he supposes a plurality of such substances - i.e. four classical elements, earth, water, air, and fire. Of these the world is built up, by the agency of two ideal motive forces - love as the cause of union, strife as the cause of separation.[14] Anaxagoras (500-428 BC) in Asia Minor also maintained the existence of an ordering principle as well as a material substance, and while regarding the latter as an infinite multitude of imperishable primary elements, he conceived divine reason or Mind (nous) as ordering them. He referred all generation and disappearance to mixture and resolution respectively. To him belongs the credit of first establishing philosophy at Athens.[14]

The Sophists held that all thought rests solely on the apprehensions of the senses and on subjective impression; therefore we have no other standards of action than convention for the individual.[14] Specializing in rhetoric, the Sophists were typically seen more as professional educators than philosophers. The Sophists traveled extensively educating people throughout Greece. Unlike philosophical schools, the sophists had no common set of philosophical doctrines that connected them to each other. They did, however, focus on teaching techniques of debate and persuasion which centered around the study of language, semantics, and grammar for use in convincing people of certain viewpoints. They also taught students their own interpretations of the social sciences, mathematics, history, among others.[22] They flourished as a result of a special need at that time for Greek education. Prominent Sophists include Protagoras (490-420 BC) from Abdera in Thrace, Gorgias (487-376 BC) from Leontini in Sicily, Hippias (485-415 BC) from Elis in the Peloponnesos, Prodicus (465-390 BC) from the island of Ceos, and Thrasymachus (459-400 BC) from Chalcedon on the Bosphorus.

Diogenes of Apollonia from Thrace (born c. 460 BC) was an eclectic philosopher who adopted many principles of the Milesian school, especially the single material principle, which he identified as air. He explained natural processes in reference to the rarefactions and condensations of this primary substance. He also adopted Anaxagoras' cosmic thought.